The field of the disclosure relates generally to motor controllers, and more particularly, to systems and methods for controlling a motor.
Motor drive systems in heating, ventilation, air-conditioning (HVAC) applications usually utilize diode/rectifier-based passive AC-DC stages and large aluminum electrolytic capacitors (i.e., 1000˜2000 microfarads) to maintain a substantially constant DC voltage. In general, pulsed current is generated from an AC power line, leading to a lower power factor (PF). Simultaneously, low frequency harmonic currents enter the electrolytic capacitors, causing increased temperatures and reduced life span. Moreover, a large dc-link capacitance usually leads to high inrush current during power-up. Passive inrush current limiters (i.e., negative temperature coefficient (NTC) thermistors) are typically provided in the AC power line to reduce inrush current, however, they also reduce overall system efficiency and long-term reliability. Also, in some applications, an external bulky and heavy power factor correction (PFC) choke is added to AC line to limit the inrush current and improve power factor, leading to higher cost and lower efficiency.